FEATURES
Battery Charger:
■
Constant-Current/Constant-Voltage Operation
with Thermal Feedback to Maximize Charge Rate
Without Risk of Overheating
■
Internal 4.5 Hour Safety Timer for Termination
■
Charge Current Programmable Up to 500mA with
5% Accuracy
■
NTC Thermistor Input for Temperature Qualified
Charging
■
C/10 Charge Current Detection Output
■
5μA Supply Current in Shutdown Mode
Switching Regulator:
■
High Efficiency Synchronous Buck Converter
■
300mA Output Current (Constant-Frequency Mode)
■
2.7V to 4.5V Input Range (Powered from BAT Pin)
■
0.8V to V
BAT
Output Range
■
MODE Pin Selects Fixed (2.25MHz) Constant-Frequency
PWM Mode or Low I
CC
(23μA) Burst Mode
®
Operation
■
2μA BAT Current in Shutdown Mode
■
10-lead, low profile (0.75 mm) 3mm
×
3mm DFN
package
LTC4081
500mA Li-Ion Charger
with NTC Input and
300mA Synchronous Buck
DESCRIPTIO
The LTC4081 is a complete constant-current/constant-
voltage linear battery charger for a single-cell 4.2V
lithium-ion/polymer battery with an integrated 300mA
synchronous buck converter. A 3mm
×
3mm DFN pack-
age and low external component count make the LTC4081
especially suitable for portable applications. Furthermore,
the LTC4081 is specifically designed to work within USB
power specifications.
The
⎯
C
⎯
H
⎯
R
⎯
G pin indicates when charge current has
dropped to ten percent of its programmed value (C/10).
An internal 4.5 hour timer terminates the charge cycle.
The full-featured LTC4081 battery charger also includes
trickle charge, automatic recharge, soft-start (to limit inrush
current) and an NTC thermistor input used to monitor
battery temperature.
The LTC4081 integrates a synchronous buck converter
that is powered from the BAT pin. It has an adjustable
output voltage and can deliver up to 300mA of load cur-
rent. The buck converter also features low-current high-
efficiency Burst Mode operation that can be selected by
the MODE pin.
The LTC4081 is available in a 10-lead, low profile (0.75
mm) 3mm
×
3mm DFN package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents,
including 6522118.
APPLICATIO S
■
■
■
■
Wireless Headsets
Bluetooth Applications
Portable MP3 Players
Multifunction Wristwatches
TYPICAL APPLICATIO
510Ω
Li-Ion Battery Charger with 1.8V Buck Regulator
100
EFFICIENCY
(Burst)
EFFICIENCY
(PWM)
80
EFFICIENCY (%)
V
CC
(3.75V
TO 5.5V)
100k
V
CC
EN_BUCK
CHRG
BAT
1OμH
SW
FB
500mA
4.7μF
60
LTC4081
NTC
4.7μF
EN_CHRG
T
+
4.2V
Li-Ion/
POLYMER
BATTERY
40
10pF
1M
V
OUT
(1.8V/300mA)
20
100k
MODE GND PROG
806Ω
806k
4081 TA01a
0
0.01
4.7μF
U
U
U
Buck Efficiency vs Load Current
(V
OUT
= 1.8V)
1000
100
POWER LOSS (mW)
POWER
LOSS 10
(PWM)
1
POWER LOSS
(Burst)
V
BAT
= 3.8V 0.1
V
OUT
= 1.8V
L = 10μH
C = 4.7μF
0.01
0.1
1
10
100
1000
LOAD CURRENT (mA)
4081 TA01b
4081f
1
LTC4081
ABSOLUTE
(Note 1)
AXI U RATI GS
BAT Short-Circuit Duration............................Continuous
BAT Pin Current ...................................................800mA
PROG Pin Current ....................................................2mA
Junction Temperature .......................................... .125°C
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Storage Temperature Range.................. – 65°C to 125°C
V
CC
, t < 1ms and Duty Cycle < 1% .............. – 0.3V to 7V
V
CC
Steady State ......................................... – 0.3V to 6V
BAT,
⎯
C
⎯
H
⎯
R
⎯
G .................................................. – 0.3V to 6V
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G, PROG, NTC ...................– 0.3V to V
CC
+ 0.3V
MODE, EN_BUCK .......................... – 0.3V to V
BAT
+ 0.3V
FB ............................................................... – 0.3V to 2V
PIN CONFIGURATION
TOP VIEW
BAT
V
CC
EN_CHRG
PROG
NTC
1
2
3
4
5
11
10 SW
9 EN_BUCK
8 MODE
7 FB
6 CHRG
DD PACKAGE
10-LEAD (3mm
×
3mm) PLASTIC DFN
T
JMAX
= 110°C,
θ
JA
= 43°C/W (NOTE 3)
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC4081EDD#PBF
TAPE AND REEL
LTC4081EDD#TRPBF
PART MARKING
LDBX
PACKAGE DESCRIPTION
10-Lead (3mm
×
3mm) DFN
TEMPERATURE RANGE
0°C to 70°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
The
●
denotes specifications which apply over the full operating tempera-
ture range, otherwise specifications are at T
A
= 25°C, V
CC
= 5V, V
BAT
= 3.8V, V
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G
= 0V, V
NTC
= 0V, V
EN_BUCK
= V
BAT
, V
MODE
= 0V.
(Note 2)
SYMBOL
V
CC
V
BAT
I
CC
I
CC_SD
PARAMETER
Battery Charger Supply Voltage
Input Voltage for the Switching
Regulator
CONDITIONS
(Note 4)
(Note 5)
●
●
●
●
ELECTRICAL CHARACTERISTICS
Quiescent Supply Current (Charger On, V
BAT
= 4.5V (Forces I
BAT
and I
PROG
= 0),
Switching Regulator Off)
V
EN_BUCK
= 0
Supply Current in Shutdown (Both
Battery Charger and Switching
Regulator Off)
V
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G
= 5V, V
EN_BUCK
= 0, V
CC
> V
BAT
V
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G
= 4V, V
EN_BUCK
= 0, V
CC
(3.5V) <
V
BAT
(4V)
2
U
W W
W
MIN
3.75
2.7
TYP
5
3.8
110
5
2
MAX
5.5
4.5
300
10
UNITS
V
V
μA
μA
μA
4081f
LTC4081
The
●
denotes specifications which apply over the full operating tempera-
ture range, otherwise specifications are at T
A
= 25°C, V
CC
= 5V, V
BAT
= 3.8V, V
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G
= 0V, V
NTC
= 0V, V
EN_BUCK
= V
BAT
, V
MODE
= 0V.
(Note 2)
SYMBOL
I
BAT_SD
PARAMETER
Battery Current in Shutdown (Both
Battery Charger and Switching
Regulator Off)
V
BAT
Regulated Output Voltage
Current Mode Charge Current
V
CC
Undervoltage Lockout Voltage
PROG Pin Servo Voltage
CONDITIONS
V
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G
= 5V, V
EN_BUCK
= 0, V
CC
> V
BAT
V
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G
= 4V, V
EN_BUCK
= 0, V
CC
(3.5V) <
V
BAT
(4V)
I
BAT
= 2mA
I
BAT
= 2mA, 4.3V < V
CC
< 5.5V
R
PROG
= 4k; Current Mode; V
EN_BUCK
= 0
R
PROG
= 0.8k; Current Mode; V
EN_BUCK
= 0
V
CC
Rising
V
CC
Falling
0.8k ≤ R
PROG
≤ 4k
●
ELECTRICAL CHARACTERISTICS
MIN
TYP
0.6
2
MAX
5
UNITS
μA
μA
Battery Charger
V
FLOAT
I
BAT
V
UVLO_CHRG
V
PROG
V
ASD
t
SS_CHRG
I
TRKL
V
TRKL
V
TRHYS
ΔV
RECHRG
ΔV
UVCL1,
ΔV
UVCL2
t
TIMER
●
●
●
●
●
●
4.179
4.158
90
475
3.5
2.8
0.98
60
15
35
4.2
4.2
100
500
3.6
3.0
1.0
82
32
180
50
2.9
150
100
300
130
4.5
2.25
1.125
0.1
115
4.221
4.242
110
525
3.7
3.2
1.02
100
45
65
3.05
350
130
V
V
mA
mA
V
V
V
mV
mV
μs
mA
V
mV
mV
mV
mV
Automatic Shutdown Threshold Voltage (V
CC
– V
BAT
), V
CC
Low to High
(V
CC
– V
BAT
), V
CC
High to Low
Battery Charger Soft-Start Time
Trickle Charge Current
Trickle Charge Threshold Voltage
Trickle Charge Threshold Voltage
Hysteresis
Recharge Battery Threshold Voltage
(V
CC
– V
BAT
) Undervoltage Current
Limit Threshold Voltage
Charge Termination Timer
Recharge Time
Low-Battery Charge Time
V
BAT
= 2.5V
R
PROG
= 2k (Note 6)
V
FLOAT
– V
BAT
, 0°C < T
A
< 85°C
I
BAT
= 0.9 I
CHG
I
BAT
= 0.1 I
CHG
●
●
●
●
V
BAT
= 2V, R
PROG
= 0.8k
V
BAT
Rising
●
2.75
100
70
180
90
3
1.5
0.75
0.085
6
3
1.5
0.115
hrs
hrs
hrs
mA/mA
°C
mΩ
Hz
%
I
C/10
T
LIM
R
ON_CHRG
f
BADBAT
D
BADBAT
I
NTC
V
COLD
V
HOT
V
DIS
f
NTC
D
NTC
End of Charge Indication Current Level
Junction Temperature in Constant-
Temperature Mode
Power FET On-Resistance (Between
V
CC
and BAT)
Defective Battery Detection
⎯
C
⎯
H
⎯
R
⎯
G Pulse
Frequency
⎯ ⎯ ⎯ ⎯
Defective Battery Detection CHRG Pulse
Frequency Duty Ratio
NTC Pin Current
Cold Temperature Fault Threshold
Voltage
Hot Temperature Fault Threshold
Voltage
NTC Disable Threshold Voltage
Fault Temperature
⎯
C
⎯
H
⎯
R
⎯
G Pulse
Frequency
⎯ ⎯ ⎯ ⎯
Fault Temperature CHRG Pulse
Frequency Duty Ratio
I
BAT
= 350mA, V
CC
= 4V
V
BAT
= 2V
V
BAT
= 2V
V
NTC
= 2.5V
Rising Voltage Threshold
Hysteresis
Falling Voltage Threshold
Hysteresis
Falling Threshold; V
CC
= 5V
Hysteresis
700
2
75
1
0.76 • V
CC
0.015 • V
CC
0.35 • V
CC
0.017 • V
CC
82
50
2
25
μA
V
V
V
V
mV
mV
Hz
%
4081f
3
LTC4081
The
●
denotes specifications which apply over the full operating tempera-
ture range, otherwise specifications are at T
A
= 25°C, V
CC
= 5V, V
BAT
= 3.8V, V
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G
= 0V, V
NTC
= 0V, V
EN_BUCK
= V
BAT
, V
MODE
= 0V.
(Note 2)
SYMBOL
Buck Converter
V
FB
I
FB
f
OSC
I
BAT_NL_CF
I
BAT_NL_BM
I
BAT_SLP
V
UVLO_BUCK
R
ON_P
R
ON_N
I
LIM_P
I
LIM_N
I
ZERO_CF
I
PEAK
I
ZERO_BM
t
SS_BUCK
Logic
V
IH
V
IL
V
OL
I
IH
I
IL
R
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G
I
⎯
C
⎯
H
⎯
R
⎯
G
Input High Voltage
Input Low Voltage
Output Low Voltage (
⎯
C
⎯
H
⎯
R
⎯
G)
Input Current High
Input Current Low
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G Pin Input Resistance
⎯
C
⎯
H
⎯
R
⎯
G Pin Leakage Current
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G, EN_BUCK, MODE Pin Low to High
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G, EN_BUCK, MODE Pin High to Low
I
SINK
= 5mA
EN_BUCK, MODE Pins at 5.5V, V
BAT
= 5V
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G, EN_BUCK, MODE Pins at GND
V
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G
= 5V
V
BAT
= 4.5V, V
⎯
C
⎯
H
⎯
R
⎯
G
= 5V
●
●
●
●
●
●
ELECTRICAL CHARACTERISTICS
PARAMETER
FB Servo Voltage
FB Pin Input Current
Switching Frequency
No-Load Battery Current (Continuous
Frequency Mode)
No-Load Battery Current (Burst Mode
Operation)
Battery Current in SLEEP Mode
Buck Undervoltage Lockout Voltage
PMOS Switch On-Resistance
NMOS Switch On-Resistance
PMOS Switch Current Limit
NMOS Switch Current Limit
NMOS Zero Current in Normal Mode
Peak Current in Burst Mode Operation
Zero Current in Burst Mode Operation
Buck Soft-Start Time
CONDITIONS
●
MIN
0.78
–50
●
TYP
0.80
2.25
1.9
23
MAX
0.82
50
2.75
UNITS
V
nA
MHz
mA
μA
V
FB
= 0.85V
No-Load for Regulator, V
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G
= 5V,
L = 10μH, C = 4.7μF
No-Load for Regulator, V
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G
= 5V,
MODE = V
BAT
, L = 10μH, C = 4.7μF
V
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G
= 5V, MODE = V
BAT
,
V
OUT
> Regulation Voltage
V
BAT
Rising
V
BAT
Falling
●
●
●
1.8
10
2.6
2.4
15
2.7
2.5
0.95
0.85
20
2.8
2.6
μA
V
V
Ω
Ω
375
520
700
15
700
mA
mA
mA
MODE = V
BAT
MODE = V
BAT
From the Rising Edge of EN_BUCK to 90%
of Buck Regulated Output
50
20
100
35
400
150
50
mA
mA
μs
1.2
0.4
60
–1
–1
1
1.45
105
1
1
3.3
1
V
V
mV
μA
μA
MΩ
μA
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
The LTC4081 is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3:
Failure to solder the exposed backside of the package to the PC
board ground plane will result in a thermal resistance much higher than
43°C/W.
Note 4:
Although the LTC4081 charger functions properly at 3.75V, full
charge current requires an input voltage greater than the desired final
battery voltage per
ΔV
UVCL1
specification.
Note 5:
The 2.8V maximum buck undervoltage lockout (V
UVLO_BUCK
) exit
threshold must first be exceeded before the minimum V
BAT
specification
applies.
Note 6:
I
C/10
is expressed as a fraction of measured full charge current
with indicated PROG resistor.
4081f
4
LTC4081
TYPICAL PERFORMANCE CHARACTERISTICS
specified)
Battery Regulation (Float) Voltage
vs Charge Current
4.21
4.20
FLOAT VOLTAGE (V)
4.19
FLOAT VOLTAGE (V)
4.18
4.17
4.16
4.15
4.14
4.13
0
50
200
150
100
CHARGE CURRENT (mA)
250
4081 G01
(T
A
= 25°C, V
CC
= 5V, V
BAT
= 3.8V, unless otherwise
Battery Regulation (Float) Voltage
vs V
CC
Supply Voltage
4.25
4.20
4.15
FLOAT VOLTAGE (V)
4.10
4.05
4.00
3.95
3.90
3.85
Battery Regulation (Float) Voltage
vs Temperature
4.210
4.205
4.200
4.195
4.190
4.185
4.180
4.175
4.170
4.165
4.160
– 50 – 30
– 10
50
30
10
TEMPERATURE (°C)
70
90
4081 G02
R
PROG
= 2k
4
4.5
5.5
V
CC
SUPPLY VOLTAGE (V)
5
6
4081 G03
Charge Current vs Temperature
with Thermal Regulation
(Constant-Current Mode)
250
V
CC
= 6V
V
BAT
= 3V
R
PROG
= 2k
1.0
PROG Pin Voltage
vs Charge Current
0.9
R
PROG
= 2k
0.8
Charger FET On-Resistance
vs Temperature
V
CC
= 4V
0.8 I
BAT
= 350mA
0.7
0.6
R
DS(ON)
(Ω)
200
CHARGE CURRENT (mA)
THERMAL CONTROL
LOOP IN OPERATION
V
PROG
(V)
150
0.6
0.5
0.4
0.3
100
0.4
50
0.2
0.2
0.1
0
–50
–25
0
25
50
75
100
125
4081 G04
0
0
25
TEMPERATURE (°C)
50 75 100 125 150 175 200
CHARGE CURRENT (mA)
4081 G05
0
– 50 – 30
–10
30
50
10
TEMPERATURE (°C)
70
90
4081 G06
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G, EN_BUCK and
MODE Pin Threshold Voltage
vs Temperature
0.95
0.90
THRESHOLD VOLTAGE (V)
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
–50
–30
–10 10
30
50
TEMPERATURE (°C)
70
90
4081 G07
⎯
E
⎯
N
⎯
_
⎯
C
⎯
H
⎯
R
⎯
G Pin Pulldown
Resistance vs Temperature
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
–50
FALLING
PULLDOWN RESISTANCE (MΩ)
RISING
–30
–10 10
30
50
TEMPERATURE (°C)
70
90
4081 G08
4081f
5
stm32/stm8
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